Infection of human coronary smooth muscle cells (SMC) with cytomegalovirus (CMV) causes generation of reactive oxygen species (ROS) and release of tumor necrosis factor-alpha(TNF). We have previously shown in CMV or TNF-activated SMC that estrogen (E, 0.1-10 nM) attenuates: 1) ROS generation, 2) Nuclear Factor (NF)kappa-B- dependent transcription of the major immediate early promoter of CMV upstream of the chloramphenicol transferase gene (MIEP-CAT), and of a 3X-kappaB-CAT reporter (containing 3-kappaB binding elements in tandem), 3) expression of protein products ICAM-1 (intercellular adhesion molecule), and of CMV-IE72 (which activates MIEP-CAT and ICAM- CAT). Although effects of E at nanomolar concentrations are due partly to direct antioxidant actions, we hypothesized that E effects on signaling mechanisms via its receptor (ER) might also play a role. To determine whether SMC might express ER, we exposed cells to E (10 nM) for 72 hours. After that we detected ERbeta , but not ERalpha(by immunocytochemistry and by Western blot). Transfection of SMC with 3X- kappaB-CAT or ICAM-CAT and the kappaB-subunit p65 caused a 10-fold or 5-fold increase, respectively, in promoter activity. By cotransfecting these SMC with increasing amounts of ERalpha , we now demonstrate that ER dose-dependently inhibits p65-dependent activation of 3X-kappaB-CAT, and of ICAM-1-CAT (contains 1 kappaB-site essential for promoter activation). The kappaB-subunit p50 was ineffective in activating the ICAM promoter. Treatment with E increased interference of ER with p65. We conclude that E may have anti-inflammatory effects due to ER- mediated interference with NF-kappaB-dependent transcription of genes that encode inflammatory proteins. - human cornary SMC, transcription factors, NF-kappaB, estrogen receptors, atherosclerosis